Near Field Communication (NFC) is a wireless communication technology that enables short-range communications between closely-positioned wireless devices. NFC operates at a frequency of 13.56 MHz, which, in many countries, falls in an unlicensed ISM (industrial, scientific, medical) frequency range. The 13.56 MHz ISM band is also used for Radio-frequency identification (RFID) applications, such as in systems compliant with the ISO/IEC 14443 standard. In fact, NFC is an extension of the RFID standard, and defines additional communication modes beyond simple RFID mechanisms. Thus, an NFC device can communicate with other NFC devices in a peer-to-peer communication mode as well as with RFID devices in a read/write mode.
Like RFID, NFC uses magnetic field induction for communication. In magnetic field induction, two communicating devices each include loop antennas. When placed in close proximity (e.g. less than 20 cm), an electrical signal on one of the loop antennas can induce an electrical signal in the other of the loop antennas, thus providing a communication path between the devices.
Generally, NFC devices can be designed communicate in a passive mode and/or an active mode. In the passive mode, the antenna of the NFC device “listens” for a 13.56 MHz signal and responds to the signal as a transponder, i.e., transmits a code in response to an interrogation signal. The NFC device may in some cases draw operating power from the electromagnetic field of the signal.
In an active mode, the NFC device may independently generate and transmit an electromagnetic signal, and subsequently listen for a response to the signal.
In the peer-to-peer communication mode, an NFC device can communicate and exchange data with another NFC device. In the read/write mode, an NFC device can read a passive device, such as an RFID tag. In either case, the NFC device may use a standard data exchange format, such as the NFC Data Exchange Format (NDEF). An NDEF message, which is the basic message format used for NFC, includes one or more NDEF records, each of which contains an NDEF payload of data.